An intermediary back-end server can facilitate information exchange between a first-party and a third-party. Generally, the intermediary back-end server uses a stable token value associated with the first-party to represent the first-party to the third-party. The stable token value may persist unchanged for a long time. The stable token value can contain information that corresponds to user-agnostic information or to user-provided information, but usually does not identify the first-party beyond the context of the information exchange. A third-party that consistently receives a stable token value may be able to determine information associated with the first-party that was not meant to be disclosed.